Method of connecting graphite articles to one another or to articles of different materials



United States Patent MEN-19D {BF CUNNECTTNG ARTECLES Tl) GNE ANQTHER 0?; T9 ARTICLES 0F DIF- FERENT MATERIALS Wilhelrnus Franciscns Knippenherg and Albert Huizing, Emmasingel, Eindhoven, Netherlands, assignors to North American Philips Company, Hue, New York, N.Y., a corporation of Delaware N0 Drawing. Filed July 23, 1962, Ser. No. 211,872

Claims priority, application Netherlands, Aug. 29, 1961,

268,735 Claims. (Cl. 29-47237) This invention relates to connecting graphite articles to one another or to articles made of different materials.

The term graphite is to be understood herein to mean not only carbon crystallized in the form of graphite, but also a material consisting in part of non-crystallized carbon, as may be the case, for example, with commercial products referred to as electrographite.

Connections to graphite articles obtained with the use of a glue on a basis of organic materials are not suitable for many uses since such connections can resist only comparatively low temperatures. Since gas-tight and liquidtight graphites are now available, tight connections are desired. Mechanical connections, for example screwed or clamped connections, are not serviceable in this case.

It is also known that connections between graphite and certain metals may be established with the use of molten metal. Such connections usually have the above-mentioned disadvantages not at all or to a reduced extent only.

Thus, it is known that such connections may be obtained with the use of indium or an indium alloy. It is also known, for example, that graphite bodies may be connected to aluminum with the use of tin. Such connections have the disadvantage, however, that indium, in dium alloys and tin have comparatively low melting points.

Known also is the use of higher melting metals or alloys, for example solder on a bases of one or more of the metals copper, silver and gold, for connecting graphite articles to other articles consisting wholly or at least at one surface of titanium, zirconium or alloys thereof. A comparatively high-melting connection is thus obtained, it is true, but the use is limited to making connections of graphite to the metals titanium and zirconium.

Finally, it is known to establish connections between graphite and metals with the use of oxides. Thus, for example, a connection between iron and graphite may be obtained by heating in an oxidizing atmosphere, the connection being established by ferric oxide produced. Such a connection has a comparatively low mechanical strength.

An object of the invention is to overcome the abovementioned disadvantages.

According to the invention, articles of graphite are connected together or to articles of other materials by soldering with an alloy of gold having a content of tantalum and/or columbium of at least 1% by weight in vacuo or in an atmosphere of inert rare gas.

Alloys having a lower content of tantalum and/or columbium provide insufficient wetting of the surfaces to be connected.

The use of a tantalum content higher than about 25% by weight, or of a columbium content higher than about 10% by weight involves the disadvantage that the alloys have melting points which are too high for easy working up, or are brittle.

Alloys having a tantalum content up to by weight and those having a columbium content up to 10% by weight have melting points lower than 1,300 C. and are 3,195,536 Patented July 27, 1965 ductile. The alloys may therefore readily be formed into wire or foil, which may be advantageous in soldering.

Very satisfactory results are obtained with alloys having a tantalum content from 5% to 10% by weight. The content of columbium is preferably chosen not higher than about 5% by weight.

Alloys of gold with tantalum and/or columbium provide very good wetting of surfaces of graphite articles in soldering. Besides, other materials of the most widely varying kinds, such as quartz, ceramics and metals, more particularly molybdenum and tungsten, are properly wetted.

In all these cases a very rigid connection is obtained which is little sensitive or not sensitive at all to variations in temperature. This is possibly due to the particular duc tility of the alloys concerned, so that stresses resulting from the different coefficients of expansion of the materials to be connected and of the alloy may readily be absorbed.

Examples (1) Two graphite tubes having an internal diameter of 8 mms. and an external diameter of 10 mms. are soldered together with an alloy consisting of by weight of gold and 5% by weight of tantalum. To this end, an annular piece of wire 200 microns thick of the alloy is brought between the ends of the tubes. Then the solder is melted in vacuo by high-frequency heating to about 1,300 C.

(2) A graphite rod of 6 mms. in diameter is soldered, at one end, to a tungsten plate with an alloy consisting of 97% by weight of gold and 3% by weight of columbium. The solder in the form of a circular piece of foil of 10 mms. in diameter and microns thick is brought between the rod and the plate. Next, heating takes place to about 1,300 C. in an atmosphere of argon.

(3) A graphite tube and a ceramic tube of alumina having the same dimensions as specified in Example 1, are connected together with the use of an alloy consisting of 97% by weight of gold and 3% by weight of tantalum. To this end, the tubes are ground at one of their ends to have a conical shape so as to fit into each other over a length of a few mms. A strip of foil 150. microns thick of the said alloy is provided between the ends of the tubes, whereupon heating takes place in vacuo to about l,300 C.

What is claimed is:

1. A method of joining graphite articles to other articles selected from the group consisting of graphite, quartz, ceramics and metals comprising applying an alloy consisting essentially of gold and a member selected from the group consisting of tantalum in an amount of from 1% to 25% by weight and columbium in an amount of from 1% to 10% by weight in contact with opposing surfaces of said articles and melting said alloy in an inert atmosphere.

2. The method of claim 1 wherein the alloy is an alloy of gold and from 1% to 25 by weight of tantalum.

3. The method of claim 1 wherein the alloy is an alloy of gold and from 5% to 10% by weight of tantalum.

4. The method of claim 1 wherein the alloy is an alloy of gold and from 1% to 10% by weight of columbium.

5. The method of claim 1 wherein the alloy is an alloy of gold and from 1% to 5% by weight of columbium.

References Cited by the Examiner UNITED STATES PATENTS 2,739,375 3/56 Coxe 29-473.1 X 2,979,813 4/61 Steinberg 29472.7 X

JOHN F. CAMPBELL, Primary Examiner. 

1. A METHOD OF JOINING GRAPHITE ARTICLES TO OTHER ARTICLES SELECTED FROM THE GROUP CONSISTING OF GRAPHITE, QUARTZ, CERAMICS AND METALS COMPRISING APPLYING AN ALLOY CONSISTING ESSENTAILLY OF GOLD AND A MEMBER SELECTED FROM THE GROUP CONSISTING OF TANTALUM IN AN AMOUNT OF FROM 1% TO 25% BY WEIGHT AND COLUMBIUM IN AN AMOUNT OF FROM 1% TO 10% BY WEIGHT IN CONTACT WITH OPPOSING SURFACES OF SAID ARTICLES AND MELTING SAID ALLOY IN AN INERT ATMOSPHERE. 